Embodiments of the present invention pertain to interconnection processing of semiconductors. Specific embodiments pertain to interconnection processes utilizing copper alloys, such as Cu—Mn, as interconnect material and the segregation of the alloying elements from the bulk copper component.
Microelectronic devices, such as semiconductors or integrated circuits, can include millions of electronic circuit devices such as transistors, capacitors, etc. To further increase the density of devices found on integrated circuits, even smaller feature sizes are desired. To achieve these smaller feature sizes, the size of conductive lines, vias, and interconnects, gates, etc. must be reduced. Reliable formation of multilevel interconnect structures is also necessary to increase circuit density and quality. Advances in fabrication techniques have enabled use of copper for conductive lines, interconnects, vias, and other structures. However, electromigration in interconnect structures becomes a greater hurdle to overcome, with decreased feature size and the increased use of copper for interconnections.
Conventional processes for forming interconnect material or interconnections include the formation of a barrier layer on a dielectric layer, deposition of a copper layer on the barrier layer and an electroplated gapfill process. More recently developed processes have incorporated dopants or alloying elements to alloy the copper layer. Interest in the use of copper alloys, such as Cu—Mn alloys, as interconnect material has been increasing due the possibility of such alloys to build a self-forming barrier that prevents interdiffusion between Cu and Si atoms. The use of Cu—Mn alloys, however, has been found to significantly increase resistivity, especially where the Cu—Mn alloy layers have been thermally annealed in oxidizing or noble gas environments. Accordingly, there is a need to reduce the high resistivity of Cu—Mn alloy interconnect material, which could cause significant increases in line resistance, and a need to control diffusion of Mn atoms into the desired interfaces to achieve a consistent performance.